As types of semiconductor devices are increased, it is required to deal with various new processes in a semiconductor manufacturing field. For example, there is a process of etching a SiO2 (silicon oxide) layer where silicon walls as pattern layers are arranged in parallel at a regular interval and an etching area is partitioned by the silicon walls and then stopping the etching in the middle of the SiO2 layer.
As for a method for etching a SiO2 layer, there is known a method disclosed in, e.g., Japanese Patent Application Publication No. 2009-158774, which performs a chemical oxide removal process using HF (hydrogen fluoride) gas and NH3 (ammonia) gas. In this method, HF gas and NH3 gas are supplied to a processing chamber while heating a semiconductor wafer (hereinafter, referred to as “wafer”) in order to etch the SiO2 layer formed on a surface of the wafer. The gases react with SiO2, thereby generating (NH4)2SiF6 (ammonium silicofluoride). SiO2 is removed by sublimating (NH4)2SiF6 by heating.
In the case of performing the process of stopping the etching of the SiO2 layer in the middle of the SiO2 layer, it is required to ensure good roughness of the surface of the SiO2 layer after the etching. In the case of etching the SiO2 layer along the pattern layers as in the above example, it is required to suppress microloading in which an etching speed varies depending on a density of the pattern.